As an atom's nucleus gets larger the electric charges repelling the protons get larger. To compensate for this greater electric charge the atom.
A.) needs more neutrons to gain enough nuclear binding forces to overcome
the repulsion.

B.) needs fewer neutrons to gain enough nuclear binding forces to overcome
the repulsion.

C.)needs more electrons to gain enough nuclear binding forces to overcome
the repulsion.

D.)needs fewer electrons to gain enough nuclear binding forces to overcome
the repulsion.

Ohm's law tells you that i = v/r where v is equivalent voltage and r is equivalent resistance of the circuit
since all circuits have the same voltage, your question is really asking which circuit has the lowest total resistance, since the lower the resistance, the higher the current
circuit a has a resistance of 5 ohms; circuit c is in series so has a resistance of 10 ohms; circuit b is in parallel and therefore has a resistance of 2.5 ohms (review your notes on adding resistances in parallel and series); therefore b has the highest current